WO2011135885A1

WO2011135885A1 - Led backlight and liquid crystal display device

Info

Publication number: WO2011135885A1
Application number: PCT/JP2011/052351
Authority: WO
Inventors: 井上　尚人; 暎冨吉; 山本　智彦
Original assignee: シャープ株式会社
Priority date: 2010-04-28
Filing date: 2011-02-04
Publication date: 2011-11-03
Also published as: US20130027288A1

Abstract

Disclosed are a direct-lighting LED backlight, and a liquid crystal display device, which is provided with the backlight. In the LED backlight, heat generated by LEDs is easily dissipated, the number of the LEDs disposed is reduced, the temperature of the LEDs does not become too high even power is concentrated on the small number of LEDs, and reliability is improved by stabilizing light emission luminance and service life. The LED backlight (BL1) is provided with: an LED substrate (2), on which a plurality of the LEDs (1) are arranged in a row in the axis line direction; and a base (3), which has a substrate attaching surface (3a) for attaching the LED substrate. The base (3) is attached to a frame (10) such that the axis line direction is in the perpendicular direction, said frame having a liquid crystal panel (6) and the LED backlight integrally assembled thereto, and a flow channel wherein air flows is provided in the perpendicular direction on the rear side of the substrate attaching surface (3a) of the base (3).

Description

LED backlight and liquid crystal display device

The present invention relates to a backlight for irradiating light from the back of a liquid crystal panel and a liquid crystal display device including the backlight, and more particularly to an LED backlight using a LED as a light source and a liquid crystal display device.

In recent years, lighting devices using LEDs (light-emitting diodes), which have long life and low power consumption and are environmentally friendly, have been put into practical use along with improvement in light emission efficiency and increase in light emission amount. Since the blue LED chip was developed, a white LED light source that emits white light by combining the blue LED chip and a phosphor that is excited by light from the LED chip and emits excitation light of a predetermined wavelength, A white LED light source that synthesizes white light using three primary color LED chips of a blue LED chip, a green LED chip, and a red LED chip has been developed.

For this reason, an LED backlight provided with this white LED light source is used as a backlight of a liquid crystal display device or the like. In addition, as a backlight of a liquid crystal display device or the like, a direct type backlight that arranges a light source on the rear surface of the display screen, a light source is arranged on the side of the display screen, and a light guide plate is installed on the rear surface of the display screen. 2. Description of the Related Art An edge-light type backlight is known in which light is incident on a light guide plate from a side portion of a display screen and light is emitted in a planar shape from a light emitting surface of the light guide plate while reflecting inside the light guide plate.

The edge-light type backlight has a light source section on the side of the display screen and a plate-shaped light guide plate installed behind the display screen, making it easy to reduce the thickness of liquid crystal display devices. preferable. In addition, the direct type backlight is preferable because a light source is installed on the rear surface of the display screen to directly illuminate, so that high-luminance illumination is easy and control of light emission luminance for each area is easy.

Moreover, in order to form a backlight with a reduced number of LEDs in a direct backlight using LEDs, a backlight having a combination of LEDs and an inclined reflecting surface is also known (for example, a patent). Reference 1). In this conventional backlight, for example, as shown in FIG. 13, an LED substrate 2C, a diffusion plate 5 and a liquid crystal panel 6 are installed on a frame 10, and both sides of the bottom surface portion where the LED 1 of the LED substrate 2C is installed are arranged. It is set as the structure which inclined and provided the reflective sheet 4C provided with reflective surface 4Ca in the surface at the side of the light emission part.

Therefore, in the liquid crystal display device 14 provided with the backlight BL4 having this configuration, the reflection surface 4Ca reflects the light emitted from the LED light source over a wide range, thereby reducing the size of the backlight. Is possible.

JP 2002-49036 A

If the number of installed LEDs is reduced, power tends to be concentrated on a small number of LEDs and the temperature tends to increase. In addition, when the temperature of the LED increases, the light emission efficiency decreases and the desired light emission luminance cannot be obtained or the life is shortened. Therefore, when the heat dissipation is poor, the life and reliability of the LED are remarkably increased. The problem of deteriorating arises.

Moreover, in order to increase the light use efficiency of the LED or to avoid a problem that foreign matter such as dust is mixed between the backlight and the liquid crystal panel and displayed on the screen, in general, The LED installation part is a hermetically sealed configuration.

Therefore, in the conventional direct type LED backlight, the heat dissipation of the LED is often poor. The above-mentioned Patent Document 1 describes that the LED and the reflecting surface are used for miniaturization, but does not describe a device for improving the heat dissipation of the LED and extending the life of the LED.

Therefore, in view of the above problems, the present invention reduces the number of installed LEDs by reducing the number of LEDs installed in a direct type LED backlight and a liquid crystal display device including the backlight as a configuration that easily dissipates heat generated by the LEDs. An object of the present invention is to provide an LED backlight that can improve the reliability by stabilizing the light emission luminance and the lifetime without causing the LED temperature to become excessively high even when power is concentrated on the LED.

In order to achieve the above object, the present invention provides an LED backlight that is attached to a frame of a liquid crystal display device including a liquid crystal panel and emits light emitted from the LED from the rear of the liquid crystal panel. A plurality of LED boards to be mounted; and a pedestal to which the LED boards are attached; a board mounting surface on which the pedestal exposes the LEDs in a light emitting region between the LEDs and the liquid crystal panel and attaches the LED boards; And a side frame portion that forms a void portion that is isolated from and not communicated with the light emitting region on the back side of the substrate mounting surface, and the pedestal so that the uniaxial direction is a vertical direction in the frame body And a vertical flow passage through which air flows is provided in the gap.

According to this configuration, even if a plurality of LEDs arranged in the vertical direction generate heat, an upward flow is generated in the vertical flow path formed on the back side of the pedestal, and a chimney effect is exhibited. Heat can be easily radiated by the flowing air. Therefore, it is possible to obtain an LED backlight in which the temperature of the LED does not become too high, and the light emission luminance and the life can be stabilized and the reliability can be improved.

In the LED backlight having the above-described configuration, the pedestal includes a board mounting surface extending in the vertical direction and side frames on both sides bent substantially at right angles from the board mounting surface. The open portion having a U-shaped cross section is used as the flow passage. According to this configuration, even if the light emitting area between the back side of the liquid crystal panel and the LED installation part is sealed, an air flow passage having a cross-section “U” is formed on the back side of the LED installation part. Air flows along the air flow passage and can easily dissipate heat.

Further, in the LED backlight having the above-described configuration, the pedestal includes a board mounting surface extending in a vertical direction and a square pipe shape having a cross-sectional shape including three side frames continuous to the board mounting surface. In addition, the hollow portion in the shape of the cross-sectional mouth is used as the flow passage. According to this configuration, even if the light emitting area between the back side of the liquid crystal panel and the LED installation part is sealed, an air flow passage having a cross-sectional “mouth shape” is formed on the back side of the LED installation part. Air flows along the air flow passage and can easily dissipate heat.

Further, the present invention provides an LED backlight having the above-described configuration, in which both sides of the pedestal sandwiching the substrate mounting surface are provided with reflecting surfaces that are inclined so as to expand toward the liquid crystal panel, and the light emitted from the LED is emitted from the LED backlight. It is characterized by a configuration that reflects toward the liquid crystal panel. According to this configuration, it is possible to irradiate a wide range, and even with a configuration in which LEDs are arranged in a vertical row, it is possible to form a display device with a large plane area, which stabilizes the light emission luminance and life. Thus, an LED backlight capable of improving reliability can be obtained.

According to the present invention, in the LED backlight having the above-described configuration, the LED irradiates a main LED arranged in parallel in a vertical direction at a predetermined pitch and a region provided on both sides of the main LED and opened at a predetermined angle. The LED group is composed of three vertical LED groups each including a second sub LED. According to this configuration, it is possible to obtain an LED backlight in which the illuminance at the side end portions on both sides, where uniform irradiation is difficult with only the main LED array, is uniform.

Further, the present invention is characterized in that in the LED backlight having the above-described configuration, a heat radiating fin is provided in the flow passage. According to this configuration, the heat dissipation performance is further improved, and even when a plurality of LEDs are used, it is possible to obtain an LED backlight that reliably dissipates heat, stabilizes light emission luminance and lifetime, and exhibits reliability.

Further, the present invention is characterized in that in the LED backlight having the above-described configuration, a slit member for suppressing entry of foreign matter is provided in the flow passage. According to this configuration, air can flow from the air intake portion while preventing insects and foreign matters from entering, and a heat dissipation effect can be exhibited by the convection action of the air.

Further, the present invention is characterized in that in the LED backlight having the above configuration, a cable wiring portion is provided in the flow path. According to this configuration, since the cable can be routed while avoiding the light emitting area, the wiring work can be easily performed, and a uniform illumination can be performed without creating a shadow on the optical part.

Further, the present invention is characterized in that a liquid crystal display device including a liquid crystal panel and the LED backlight according to any one of claims 1 to 8 is provided. According to this configuration, it is possible to obtain a liquid crystal display device that can improve the reliability by stabilizing the light emission luminance and the lifetime. In addition, a liquid crystal display device that can be reduced in size by reducing the number of installed LEDs can be obtained.

According to the present invention, the LEDs are installed at a predetermined pitch above and below the pedestal in the vertical direction, and the vertical air flow passage is formed on the back side of the pedestal. Therefore, even if the LED generates heat, it is formed on the back side of the pedestal. The air flows along the vertical flow path and can easily dissipate heat. Therefore, even if the number of LEDs is reduced and power is concentrated on this small number of LEDs, the temperature of the LEDs does not become too high, and it is possible to stabilize the light emission luminance and life and improve the reliability. An LED backlight can be obtained.

It is a schematic explanatory drawing which shows a liquid crystal display device provided with the LED backlight of 1st embodiment which concerns on this invention. It is a principal part enlarged view of the LED backlight of 1st embodiment. It is a principal part expansion perspective view of the LED backlight of 1st embodiment. It is a principal part expansion perspective view which shows the back side of FIG. It is a schematic explanatory drawing which shows a liquid crystal display device provided with the LED backlight of 2nd embodiment. It is a principal part expansion perspective view which shows the modification of the LED backlight of 1st embodiment. It is a schematic explanatory drawing which shows an example of the air intake member which has many small holes. It is a schematic explanatory drawing which shows an example of the air intake member which has many slot-shaped opening. It is a schematic explanatory drawing which shows a liquid crystal display device provided with the LED backlight of 3rd embodiment. It is a principal part enlarged view of the LED backlight shown in FIG. It is a schematic perspective view which shows the modification which utilizes a space | gap part as a cable insertion part. It is a principal part enlarged view of the LED backlight of a modification provided with LED group of 3 vertical rows. It is a figure which shows the light intensity characteristic calculated | required of the LED light source with respect to an irradiation angle. It is a figure which shows an example of the light intensity distribution on the backlight surface at the time of using only main LED. It is a figure which shows an example of the light intensity distribution on the backlight surface at the time of using only sub LED. It is a figure which shows an example of the light intensity distribution on the backlight surface at the time of using both main LED and sub LED simultaneously. It is a schematic explanatory drawing which shows the structure of the conventional LED backlight.

Embodiments of the present invention will be described below with reference to the drawings. Moreover, the same code | symbol is used about the same structural member, and detailed description is abbreviate | omitted suitably.

First, an example of an LED backlight according to the present invention will be described with reference to FIG.

FIG. 1 shows a liquid crystal display device 11 including the LED backlight BL1 of the first embodiment. The LED backlight BL1 includes a LED board 2 in which a plurality of LEDs 1 are arranged in a uniaxial direction, and a base 3 having a board mounting surface 3a to which the LED board 2 is attached. The LED backlight BL1 A liquid crystal display device 11 is configured by integrally assembling the diffusion plate 5 and the liquid crystal panel 6 to the frame body 10.

FIG. 1 is a plan view of the liquid crystal display device 11, and the pedestal 3 is attached to the frame 10 so that the uniaxial direction is a vertical direction as shown in FIG. For this purpose, a plurality of LEDs 1 are arranged above and below in the vertical direction, and the pedestal 3 has a substrate mounting surface 3a and a side wall portion that forms a gap on the back side of the substrate mounting surface 3a. A flow passage through which air flows is provided in the gap. In addition, in order to illuminate the liquid crystal panel 6 over a wide range via a plurality of LEDs 1 arranged in a vertical line in the vertical direction, a configuration in which a reflection member 4 that reflects light emitted from the LEDs 1 toward the diffusion plate 5 is provided. The LED backlight BL1 may be used.

The diffusion plate 5 is a thin plate-like or film-like optical member that diffuses the light emitted from the LED 1 and spreads the light over the entire area of the liquid crystal panel 6.

The liquid crystal panel 6 has a configuration in which a liquid crystal material is enclosed between two transparent glass substrates in a sandwich shape, and a color filter and a polarizing filter are laminated, and is formed in a lattice shape via switching elements formed in a lattice shape. A large number of pixels are formed, and the liquid crystal orientation is changed by changing the voltage supplied to each switching element, and the amount of light transmitted through each pixel is controlled to display a predetermined image on the upper surface of the liquid crystal panel 6. It is configured.

The light emitting area between the LED 1 and the liquid crystal panel 6 is generally hermetically sealed in order to increase the light use efficiency of the LED 1 and to avoid a problem that foreign matter such as dust is mixed and displayed on the screen. It is the structure which was made. Therefore, the light emitting area where the LED 1 is installed is a sealed space 9. In the drawing, for the sake of convenience, the respective members are shown separated from each other, and it appears that they are not sealed, but this light emitting region is actually sealed.

Further, as shown in FIG. 2, a plurality of LEDs 1 are arranged in a vertical row at a predetermined pitch on a pedestal 3 having a shape extending in the vertical direction. The pedestal 3 is, for example, a U-shaped pedestal having an LED board mounting surface 3a and

side frames

3b and 3b on both sides bent substantially at right angles from the LED board mounting surface 3a as shown in the figure. Therefore, the side frames 3b and 3b can be used as a side frame portion that forms a gap portion that is isolated from and does not communicate with the light emitting region, and is a gap extending in the vertical direction, that is, the vertical direction on the back side of the LED board mounting surface 3a. The part 7 can be formed.

Therefore, when the LED 1 emits light and generates heat, the air on the back side of the LED 1 is warmed to generate an upward air flow, and a flow passage is formed in the gap portion 7 through which the air from the bottom to the top flows. That is, the gap 7 becomes an air flow passage having a cross-section “U-shape”.

Moreover, since this space | gap part 7 becomes another space which was isolated from the sealed space 9 between the liquid crystal panel 6 and LED1 and does not communicate, it is not necessary to seal, but it can be made into the open space connected to external air. . That is, when air flows through the gap portion 7, the heat generated by the LED 1 can be radiated by the convection action of the air, and the abnormal temperature rise of the LED 1 can be suppressed. Therefore, a configuration in which a vertical air flow passage is provided on the back side of the LED board mounting surface 3a is preferable as a heat dissipation structure capable of exhibiting a chimney effect.

As described above, the frame 10 that integrally mounts the liquid crystal panel 6 and the LEDs 1, the pedestal 3 that extends vertically above and below the frame 10, and the plurality of LEDs 1 that are attached to the pedestal 3 vertically LED board 2 mounted at a predetermined pitch in the direction, and by providing a flow path through which air flows on the back side of the LED board mounting surface of pedestal 3, the pedestal 3 is arranged side by side in the vertical direction. Even if the LED 1 generates heat, air flows along a vertical air flow passage formed on the back side of the pedestal 3 and can easily dissipate heat. For this reason, the LED backlight BL1 can be obtained in which the temperature of the LED 1 does not become excessively high, the light emission luminance and the lifetime are stabilized and the reliability can be improved, and the LED backlight is provided in a wide range. By illuminating, it is possible to obtain the liquid crystal display device 1 with improved reliability by reducing the size and stabilizing the luminance and life.

In addition, a reflecting member 4 having a reflecting surface 4a inclined so as to expand toward the liquid crystal panel 6 is provided on both sides of the pedestal 3 sandwiching the substrate mounting surface 3a, and the light emitted from the LED 1 is reflected toward the liquid crystal panel 6. It is preferable to adopt a configuration to do so. With this configuration, it is possible to illuminate a wide range in the horizontal direction via the LED 1 installed in the substantially central portion behind the liquid crystal panel 6, and even if the configuration is such that the LEDs 1 are arranged in a vertical row, A display device can be formed. Therefore, the LED can be adapted to the liquid crystal panel 6 having a large area with a small number of LEDs, and the display device can be further miniaturized, and the light emission luminance and the life can be stabilized to improve the reliability. The backlight BL1 can be obtained.

The reflection member 4 only needs to have a reflection surface 4a that exhibits a high reflectivity with respect to the light emitted from the LED 1. For example, if the LED 1 is a white LED light source, the reflection member 4 is configured of a member that efficiently reflects visible light. can do. Alternatively, a configuration may be adopted in which a reflective film made of a polyester resin used for efficiently reflecting visible light (approximately 400 to 800 nm) is attached to a member such as a resin.

As shown in FIGS. 3 and 4, the pedestal 3 is preferably a pedestal 3 having a U-shaped cross section. At this time, the open portion having a U-shaped cross section becomes the gap portion 7. Thus, the light emitting region between the back side of the liquid crystal panel and the LED installation portion is formed by using the air gap 7 as an air flow path as a U-shaped cross section having the air gap 7 above and below in the vertical direction. Even in a sealed space, a vertical air flow passage having a cross-section “U” shape is formed on the back side of the LED installation portion, and air flows along this air flow passage and easily dissipates heat by air convection. be able to.

The backlight BL1 shown in FIG. 3 is a backlight that can be used for a liquid crystal display device such as a small TV, for example, and a plurality of LEDs 1 are disposed at the rear of the display screen. Moreover, even if it is the structure which is equipped with the reflective member 4 which inclines toward the display screen on both sides of the side part of the base 3, and arrange | positions LED in the vertical line of the vertical direction of a center part, it is far The entire area of the display screen with a large area can be illuminated.

In the backlight BL1 having a pedestal 3 having a U-shaped cross section, as shown in FIG. 4, the back side portion of the LED board mounting surface 3a is an open portion, and this open portion is used as air for cooling air. It can be used as an air flow passage.

Further, if the pedestal 3 is a good heat conductor, heat is conducted from the LED board 2 on which the LED 1 is mounted to the pedestal 3, so that the air flow D 1 flowing through the gap 7 serving as an air flow passage is efficient. It can dissipate heat. Therefore, the pedestal 3 is preferably made of a sheet metal or a hard resin having thermal conductivity.

The shape of the pedestal may be other than the above-described U-shaped cross section, for example, a cross-sectional mouth shape. For this purpose, an LED backlight BL2 will be described with reference to FIG.

FIG. 5 shows a liquid crystal display device 12 including the LED backlight BL2, the diffusion plate 5, and the liquid crystal panel 6 of the second embodiment. Similarly to the backlight BL1 of the first embodiment described above, the LED backlight BL2 also has an LED board 2 on which the LED 1 is mounted on the frame 10, a pedestal on which the LED board 2 is mounted, and the light emitted by the LED 1. In this configuration, a reflecting member 4A having a reflecting surface 4Aa that reflects toward the diffusion plate 5 is provided.

However, the difference is that the pedestal is a square pipe-shaped pedestal 3 A having gaps in the vertical direction. For this purpose, the pedestal 3A of the present embodiment is an LED board mounting surface 3Aa and a rectangular shape with a cross-sectional mouth shape including three side frames connected to the LED substrate mounting surface, and the hollow portion in the center is air circulation. It becomes a gap portion 7A that becomes a road.

If it is said structure, even if it is the space which sealed the light emission area | region between the back side of the liquid crystal panel 6 and LED installation part, the cross-section "mouth shape" airflow path is formed in the back side of LED installation part. Therefore, air flows along this air flow passage and can be easily dissipated. That is, the heat of the LED 1 and the LED substrate 2 can be radiated by the chimney effect of the gap 7A.

Further, the square pipe-shaped pedestal 3A can be provided so as to protrude from the reflecting member 4A to the inside of the sealed space 9, and the thickness of the liquid crystal display device 12 is not increased. Therefore, even if it is a structure provided with the square pipe-shaped base 3A, the liquid crystal display device 12 can be reduced in thickness without becoming thick.

As described above, since the gap 7A is not separated from the sealed space 9 and is an isolated and independent space, the gap 7A is communicated with the outside air and used as an air flow passage for air cooling. Can do. Therefore, this gap 7A can be used as a heat radiating means that exhibits a chimney effect.

Moreover, in order to improve heat dissipation, it is possible to provide a heat dissipating fin in the air flow path, whether it is the square pipe-shaped base 3A or the base 3 having a U-shaped cross section. For example, the liquid crystal display device 13 shown in FIG. 7 includes an LED backlight BL3 having a configuration in which a plurality of plate-like heat radiation fins 21 extending in the vertical direction of the gap 7 (the direction penetrating the paper surface in the drawing) are provided. It is set as the structure provided with.

In the case of the LED backlight BL3 having the above-described configuration, the entire surface of the heat radiating fins 21 becomes a heat radiating surface, so that the heat radiating area can be increased and the heat radiating property can be enhanced. Moreover, if it is the structure provided with the plate-shaped fin in the perpendicular direction of the space | gap part 7, since the several plate-shaped fin will exhibit the effect | action of the baffle plate which rectifies | straightens the flow of air, the air in this space | gap part 7 will be demonstrated. Can be made to flow smoothly, and heat dissipation is further improved.

For example, as shown in FIG. 8, rectifying paths A 1, A 2, A 6 are formed between the side frames 3 b, 3 b of the base 3 by the radiation fins 21 provided in the gap 7. As described above, if the heat dissipation fin 21 is provided in the air flow path, the heat dissipation performance is further improved, and even if a plurality of LEDs are used, the heat is reliably radiated to stabilize the light emission luminance and life. LED backlight BL3 which exhibits high reliability can be obtained.

As shown in FIG. 6A, a slit member 8A is provided in the gap 7 of the pedestal 3 to form an air intake so that air can flow but insects such as cockroaches and dust do not enter. Good. If it is LED backlight BL1A of such a structure, air will flow in from an air intake part, preventing the penetration | invasion of an insect and a foreign material, and can exhibit the thermal radiation effect by the convection effect | action of air.

Further, instead of the slit member 8A, an air intake member 8B having many small holes as shown in FIG. 6B or an air intake member 8C having many elongated holes as shown in FIG. 6C may be provided. . For these air intake members, punching metal made of various materials, resin processed products, or the like can be used.

Moreover, as shown in FIG. 9, if the space | gap part 7 is provided in the back side of the LED board attachment part 3a, this space | gap part 7 can be utilized as a cable insertion part. At this time, the LED backlight BL1B having a configuration in which the slit member 8A is provided as an air intake member is preferable because it does not obstruct the insertion of the cable K.

If the cable K is inserted into the gap 7, the cable K is inserted through a portion irrelevant to the light emitting region where the backlight is irradiated or emitted, so that no optical shadow is produced and uniform. Backlight irradiation is possible.

Moreover, since wiring is possible along the back side of the LED substrate 2, even a configuration including a large number of LEDs 1 is preferable because wiring is easy.

As described above, if the cable wiring portion is provided in the air flow path, the cable K can be routed while avoiding the light emitting area, so that the wiring work can be easily performed and the optical portion is not shaded and is uniform. Lighting is possible.

Next, with reference to FIGS. 10, 11, and 12A to 12C, a modification of the LED backlight having a configuration in which a sub LED is provided on the side of the main LED in addition to the central main LED will be described.

The LED backlight BL1C shown in FIG. 10 includes, as LEDs, a main LED 1A arranged in parallel at a predetermined pitch in the vertical direction (direction penetrating through the paper surface in the drawing) of the central portion in the axial direction of the base 3, and the main LED 1A. It is the structure provided with 1st sub LED1B and 2nd subLED1C which are provided in both sides and irradiate the area | region which opened each predetermined angle, respectively. If it is this structure, it will become possible to irradiate at a wide angle from the LED group arrange | positioned by the vertical direction at three vertical rows.

This LED backlight BL1C is covered by the main LED 1A because it is difficult to cover the light intensity distribution up to 90 ° (-90 ° to + 90 °) on both sides with one main LED 1A in the center as needed. In order to compensate for the light intensity at both ends that cannot be reached, auxiliary sub-LEDs 1B and 1C are arranged on the left and right sides of the main LED 1A. This is preferable because the surface distribution of the backlight light can be made wider and more uniform.

For example, in the LED backlight BL1 having a configuration in which a plurality of LEDs 1 are arranged in a vertical line as shown in FIG. 1 and illuminates in a wide range via the reflecting member 4, the diffuser plate 5 is uniformly irradiated with the backlight light. Therefore, the emission intensity characteristic of the LED 1 (corresponding to the main LED 1A) required for this is the light intensity H1 indicated by the solid line in FIG.

As shown by the light intensity H1, more uniform backlight illumination can be achieved by increasing the light intensity in the region diffused by ± 60 ° compared to the light intensity at the center. Further, when illuminating in a wider range (at a wide angle), as indicated by a broken line in the figure, the light intensity H2 is irradiated through the first sub LED, and the light intensity H3 is transmitted through the second sub LED. It is good to perform irradiation.

12A to 12C show the light intensity distribution on the backlight surface having the width L. FIG. 12A shows the light intensity distribution K1 obtained when only the main LED is turned on, FIG. 12B shows the light intensity distribution K2 obtained when only the sub LED is turned on, and FIG. 12C shows both the main LED and the sub LED. The light intensity distribution K3 obtained when is simultaneously turned on. This light intensity distribution K3 is the sum of the light intensity distribution K1 and the light intensity distribution K2 (K1 + K2).

As is clear from this figure, when only the main LED is lit, the light intensity at the end is lower than the central portion in the width direction of the backlight surface, but the main LED and the sub LED are shared. Thus, the light intensity on the backlight surface can be made substantially uniform.

As described above, LEDs used in a direct type backlight having a configuration in which a plurality of LEDs are arranged in the vertical direction in the central part at the rear of the liquid crystal panel are arranged in parallel at predetermined pitches in the vertical direction at the central part at the rear of the liquid crystal panel. It is preferable that the main LED includes a vertical three-row LED group including first and second sub-LEDs that irradiate a region that is provided on both sides of the main LED and that is open at a predetermined angle. If it is this structure, the LED backlight which improved the uniformity of the light intensity of the both sides of a display screen which is difficult only by the main LED row | line | column can be obtained.

Although the example which consists of LED group of the above-mentioned three vertical rows is an example which used reflection member 4, depending on the size of LED which irradiates with a wide angle, and LED backlight, without using reflection member 4, It is possible to make the light intensity on the backlight surface substantially uniform by using only the three vertical LED groups.

As described above, according to the present invention, a plurality of LEDs are installed at a predetermined pitch above and below the pedestal to which the LED substrate is attached, and a vertical air flow passage is formed on the back side of the pedestal. Even if the LED generates heat, air flows along a vertical flow path formed on the back side of the pedestal and can easily dissipate heat. Therefore, it is possible to obtain an LED backlight in which the temperature of the LED does not become too high, and the light emission luminance and the life can be stabilized and the reliability can be improved.

In addition, by providing a reflective surface that is inclined so as to extend in the direction toward the liquid crystal panel on both sides of the pedestal, it is possible to illuminate a wide area using the light emission of the LED, and the LEDs are arranged in a vertical row. Even with the installed configuration, it is possible to form a large flat area lighting device (backlight), and to obtain an LED backlight that can stabilize the light emission luminance and life and improve the reliability. be able to.

Thus, even if the LED backlight according to the present invention has a configuration in which a plurality of LEDs are vertically arranged in parallel, it has a configuration in which a gap portion serving as an air flow passage is provided on the back side of the pedestal for mounting the LED substrate. It becomes possible to dissipate the heat generated by the LED, and the life and reliability of the LED can be improved.

In addition, even if the number of LEDs is reduced and power is concentrated on this small number of LEDs, the temperature of the LEDs does not become too high, and it is possible to stabilize the light emission luminance and life and improve the reliability. A backlight can be obtained.

Therefore, the LED backlight according to the present invention is suitable for an LED backlight of a liquid crystal display device that can stabilize the light emission luminance and life and improve the reliability even if the number of LEDs is reduced. Will be available.

1 LED
1A Main LED
1B, 1C sub LED
2

LED board

3, 3A base 3a, 3Aa board mounting surface 3b side frame 4 reflecting member 4a reflecting surface 5 diffusion plate 6

liquid crystal panel

7, 7A gap (air flow path)
10

Frame

11, 12, 13 Liquid crystal display device (of the present invention)
14 Liquid crystal display (conventional)
BL1 LED backlight (first embodiment)
BL2 LED backlight (second embodiment)
BL3 LED backlight (third embodiment)
BL4 LED backlight (conventional)
21 Radiation fin D1 Air flow

Claims

In an LED backlight that is attached to a frame of a liquid crystal display device including a liquid crystal panel and emits light emitted from the LED from the rear of the liquid crystal panel,
An LED board on which a plurality of the LEDs are mounted in a uniaxial direction, and a pedestal for mounting the LED board;
The pedestal exposes the LED in a light emitting region between the LED and the liquid crystal panel and attaches the LED substrate, and the light emitting region is separated from the light emitting region on the back side of the substrate mounting surface and does not communicate with the substrate mounting surface. As a configuration having a side frame portion that forms a void portion,
An LED backlight, wherein the pedestal is attached to the frame body so that the uniaxial direction is a vertical direction, and a vertical flow passage through which air flows is provided in the gap.
The pedestal includes a board mounting surface extending in the vertical direction and side frames on both sides bent at substantially right angles from the board mounting surface. The LED backlight according to claim 1, wherein the flow passage is used.
The pedestal has a square pipe shape with a cross-sectional mouth shape including a substrate mounting surface extending in the vertical direction and three side frames continuous to the substrate mounting surface. The LED backlight according to claim 1, wherein the LED passage is used.
Reflecting surfaces that are inclined so as to spread in the direction toward the liquid crystal panel are provided on both sides of the base mounting surface of the pedestal, and the light emitted from the LEDs is reflected toward the liquid crystal panel. The LED backlight according to any one of claims 1 to 3.
The LEDs are arranged in three vertical rows, each having a main LED arranged in parallel in the vertical direction at predetermined pitches, and first and second sub-LEDs that are provided on both sides of the main LED and irradiate a region opened by a predetermined angle. The LED backlight according to claim 1, comprising an LED group.
The LED backlight according to claim 1, wherein a heat radiating fin is provided in the flow path.
The LED backlight according to claim 1, wherein a slit member that suppresses intrusion of foreign matter is provided in the flow passage.
The LED backlight according to claim 1, wherein a cable wiring portion is provided in the flow path.
A liquid crystal display device comprising a liquid crystal panel and the LED backlight according to claim 1.